U.S. patent number 6,628,328 [Application Number 09/161,585] was granted by the patent office on 2003-09-30 for image pickup apparatus having a cpu driving function operable in two modes.
This patent grant is currently assigned to Olympus Optical Co., Ltd.. Invention is credited to Takayuki Kijima, Yoshitaka Ogawa, Junzo Sakurai, Masaki Yokouchi.
United States Patent |
6,628,328 |
Yokouchi , et al. |
September 30, 2003 |
Image pickup apparatus having a CPU driving function operable in
two modes
Abstract
In an image pickup apparatus comprising a CCD image pickup
device made up of a plurality of pixels constituted by photodiodes
which are two-dimensionally arrayed, a vertical register and a
horizontal register, and a CPU for driving and controlling the CCD
image pickup device, the CPU has a driving function in an all-pixel
read mode for reading pixel signals from all the pixels of the CCD
image pickup device, a driving function in a thinning (skipping)
read mode for reading pixel signals from all the pixels in a
thinned-out fashion, and a device shutter function for extracting
signal electric charges from each pixel to control an exposure
time. In the thinning read mode, the operation of extracting the
signal electric charges from each pixel is carried out one or more
times for each read period of one frame.
Inventors: |
Yokouchi; Masaki (Kokubunji,
JP), Kijima; Takayuki (Akiruno, JP),
Sakurai; Junzo (Koganei, JP), Ogawa; Yoshitaka
(Hachioji, JP) |
Assignee: |
Olympus Optical Co., Ltd.
(Tokyo, JP)
|
Family
ID: |
17633967 |
Appl.
No.: |
09/161,585 |
Filed: |
September 28, 1998 |
Foreign Application Priority Data
|
|
|
|
|
Sep 30, 1997 [JP] |
|
|
9-281074 |
|
Current U.S.
Class: |
348/221.1;
348/296; 348/312; 348/317; 348/364; 348/E5.037; 348/E5.091;
348/E5.047; 348/E3.02 |
Current CPC
Class: |
H04N
5/343 (20130101); H04N 5/3728 (20130101); H04N
5/335 (20130101); H04N 5/3456 (20130101); H04N
5/2353 (20130101); H04N 5/369 (20130101) |
Current International
Class: |
H04N
5/235 (20060101); H04N 3/15 (20060101); H04N
5/335 (20060101); H04N 5/232 (20060101); H04N
003/14 (); H04N 005/235 (); H04N 005/238 () |
Field of
Search: |
;348/207,220,221,222,240,294-304,307-312,315-319,362,363,364,222.1,229.1,230.1
;250/208.1 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Vu; Ngoc-Yen
Attorney, Agent or Firm: Armstrong, Westerman & Hattori,
LLP.
Claims
What is claimed is:
1. An image pickup apparatus comprising a solid state image pickup
device made up of a plurality of pixels constituted by
photoelectric transducers which are two-dimensionally arrayed in
the horizontal and vertical directions, a vertical register for
receiving signal electric charges of each pixel and transferring
the signal electric charges in the vertical direction, and a
horizontal register for transferring the signal electric charges in
said vertical register in the horizontal direction, and control
means for driving and controlling said solid state image pickup
device, wherein said control means has a driving function in an
all-pixel read mode for transferring the signal electric charges
from all the pixels of said solid state image pickup device to said
vertical registers to read pixel signals, a driving function in a
thinning read mode for transferring the signal electric charges
from a number n (n is one or more positive integer) of pixels for
each unit of a number m (m is two or more positive integer) of
pixels in the vertical direction to said vertical registers to read
pixel signals, and a device shutter function for extracting the
signal electric charges from each pixel to control a photoelectric
conversion time, said control means being designed in the thinning
read mode to carry out the operation of extracting the signal
electric charges from each pixel one or more times for each read
period of one frame.
2. An image pickup apparatus comprising a solid state image pickup
device made up of a plurality of pixels constituted by
photoelectric transducers which are two-dimensionally arrayed in
the horizontal and vertical directions, a vertical register for
receiving signal electric charges of each pixel and transferring
the signal electric charges in the vertical direction, and a
horizontal register for transferring the signal electric charges in
said vertical register in the horizontal direction, and control
means for driving and controlling said solid state image pickup
device, wherein said control means has a driving function in an
all-pixel read mode for transferring the signal electric charges
from all the pixels of said solid state image pickup device to said
vertical registers to read pixel signals, a driving function in a
thinning read mode for transferring the signal electric charges
from a number n (n is one or more positive integer) of pixels for
each unit of a number m (m is two or more positive integer) of
pixels in the vertical direction to said vertical registers to read
pixel signals, and a device shutter function for extracting the
signal electric charges from each pixel to control a photoelectric
conversion time, said control means being designed to carry out the
operation of extracting the signal electric charges from each pixel
one or more times immediately before the start of exposure when
said solid state image pickup device is driven in the all-pixel
read mode directly subsequent to the thinning read mode.
3. An image pickup apparatus comprising a solid state image pickup
device made up of a plurality of pixels constituted by
photoelectric transducers which are two-dimensionally arrayed in
the horizontal and vertical directions, a vertical register for
receiving signal electric charges of each pixel and transferring
the signal electric charges in the vertical direction, and a
horizontal register for transferring the signal electric charges in
said vertical register in the horizontal direction, and control
means for driving and controlling said solid state image pickup
device, wherein said control means has a driving function in an
all-pixel read mode for transferring the signal electric charges
from all the pixels of said solid state image pickup device to said
vertical registers to read pixel signals, a driving function in a
thinning read mode for transferring the signal electric charges
from a number n (n is one or more positive integer) of pixels for
each unit of a number m (m is two or more positive integer) of
pixels in the vertical direction to said vertical registers to read
pixel signals, and a device shutter function for extracting the
signal electric charges from each pixel to control a photoelectric
conversion time, said control means being designed to transfer the
signal. electric charges from all the pixels to said vertical
registers at the beginning of the read period of one frame
immediately before starting to read the pixel signals of all the
pixels when said solid state image pickup device is driven in the
all-pixel read mode directly subsequent to the thinning read
mode.
4. An image pickup apparatus comprising a solid state image pickup
device made up of a plurality of pixels constituted by
photoelectric transducers which are two-dimensionally arrayed in
the horizontal and vertical directions, a vertical register for
receiving signal electric charges of each pixel and transferring
the signal electric charges in the vertical direction, and a
horizontal register for transferring the signal electric charges in
said vertical register in the horizontal direction, and control
means for driving and controlling said solid state image pickup
device, wherein said control means has a driving function in an
all-pixel read mode for transferring the signal electric charges
from all the pixels of said solid state image pickup device to said
vertical registers to read pixel signals, a driving function in a
thinning read mode for transferring the signal electric charges
from a number n (n is one or more positive integer) of pixels for
each unit of a number m (m is two or more positive integer) of
pixels in the vertical direction to said vertical registers to read
pixel signals, and a device shutter function for extracting the
signal electric charges from each pixel to control a photoelectric
conversion time, said control means being designed to transfer the
signal electric charges from all the pixels to said vertical
registers and then transfer the signal electric charges in said
vertical registers at a high speed immediately before starting to
read the pixel signals of all the pixels when said solid state
image pickup device is driven in the all-pixel read mode directly
subsequent to the thinning read mode.
5. An image pickup apparatus comprising a solid state image pickup
device made up of a plurality of pixels constituted by
photoelectric transducers which are two-dimensionally arrayed in
the horizontal and vertical directions, a vertical register for
receiving signal electric charges of each pixel and transferring
the signal electric charges in the vertical direction, and a
horizontal register for transferring the signal electric charges in
said vertical register in the horizontal direction, and control
means for driving and controlling said solid state image pickup
device, wherein said control means has a device shutter function
for extracting signal electric charges from each pixel to control a
photoelectric conversion time, performs the operation of extracting
the signal electric charges from each pixel a number n (n is one or
more positive integer) time(s) immediately before the start of
exposure during a read period in which an output of the solid state
image pickup device is used to form a motion picture, and performs
the operation of extracting the signal electric charges from each
pixel repeatedly to inhibit an exposure operation during a read
period in which an output of said solid state image pickup device
is used to form a still picture.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image pickup apparatus
including drive/control means operated in an all-pixel read mode
for reading pixel signals from all pixels and a thinning read mode
for reading pixel signals from all pixels in a thinned-out fashion,
and more particularly to an image pickup apparatus capable of being
smoothly switched over in operation between the thinning read mode
and the all-pixel read mode.
2. Description of the Related Art
Recently, with image pickup apparatus using CCD image pickup
devices, which are utilized in electronic cameras or the like,
constructed of a large number of pixels, the apparatus has been
designed to read pixels in a skipping fashion, i.e., in a
thinned-out fashion, without reading all the pixels except
recording of a still picture, for thereby achieving high-speed
processing that is required, e.g., when an image is to be displayed
in a liquid crystal display unit, and when the AE or AF operation
is to be carried out. By operating the image pickup apparatus in
such a thinning read mode, pixel signals can be read at a higher
speed than an all-pixel read mode because all the pixels are not
read in the thinning read mode. In the liquid crystal display unit,
for example, the number of frames displayed per second can be
increased, and therefore a smooth motion picture can be displayed
rather than an intermittent frame picture.
When a CCD image pickup device is driven in the skipping read mode
(thinning read mode), some of pixel lines are read, but the
remaining pixel lines are not read. Then, if exposure is repeated
many times for the pixel lines which are not read, signal electric
charges may overflow from photodiodes constituting pixels of those
lines and may mix into transfer lines. Also, in image pickup
apparatus operated in the skipping read mode and the all-pixel read
mode, when the operating mode is shifted from the skipping read
mode to the all-pixel read mode, there arises a similar problem.
Specifically, if signal electric charges overflow in some lines
which are subjected to multiple exposures in the skipping read
mode, the signal electric charges generated in the skipping read
mode and still remained in the pixels of those lines may mix in
signal electric charges generated in the all-pixel read mode.
SUMMARY OF THE INVENTION
The present invention has been made with a view of solving the
above-mentioned problems in the conventional image pickup apparatus
including drive/control means operated in a thinning read mode and
an all-pixel read mode, and a main object of the present invention
is to provide an image pickup apparatus which can prevent signal
electric charges from overflowing in the thinning read mode, can
hence eliminate the need of interlaced scanning, and is free from
flickers.
According to the present invention, in an image pickup apparatus
comprising a solid state image pickup device made up of a plurality
of pixels constituted by photoelectric transducers which are
two-dimensionally arrayed in the horizontal and vertical
directions, a vertical register for receiving signal electric
charges of each pixel and transferring the signal electric charges
in the vertical direction, and a horizontal register for
transferring the signal electric charges in the vertical register
in the horizontal direction, and control means for driving and
controlling the solid state image pickup device, the control means
has a driving function in an all-pixel read mode for transferring
the signal electric charges from all the pixels of the solid state
image pickup device to the vertical registers to read pixel
signals, a driving function in a thinning read mode for
transferring the signal electric charges from a number n (n is one
or more positive integer) of pixels for each unit of a number m (m
is two or more positive integer) of pixels in the vertical
direction to the vertical registers to read pixel signals, and a
device shutter function for extracting the signal electric charges
from each pixel to control a photoelectric conversion time, the
control means being designed in the thinning read mode to carry out
the operation of extracting the signal electric charges from each
pixel one or more times for each read period of one frame.
By carrying out the operation of extracting the signal electric
charges from each pixel one or more times for each read period of
one frame when the solid state image pickup device is driven in the
thinning read mode, it is possible to prevent overflow of signal
electric charges from the pixels, from which the signal electric
charges are not read, the overflow being otherwise caused during
the operation in the thinning read mode. There can be thus provided
an image pickup apparatus in which even when the same pixels are
read repetitively during the operation in the thinning read mode,
overflow of signal electric charges from the pixels which are not
read can be prevented; hence interlaced scanning is no longer
needed and the occurrence of flickers is avoided.
Another object of the present invention is to provide an image
pickup apparatus which can prevent, at the time of shift from the
thinning read mode to the all-pixel read mode, the signal electric
charges remained in the thinning read mode from mixing in the
all-pixel read mode.
According to the present invention, in an image pickup apparatus
comprising a solid state image pickup device made up of a plurality
of pixels constituted by photoelectric transducers which are
two-dimensionally arrayed in the horizontal and vertical
directions, a vertical register for receiving signal electric
charges of each pixel and transferring the signal electric charges
in the vertical direction, and a horizontal register for
transferring the signal electric charges in the vertical register
in the horizontal direction, and control means for driving and
controlling the solid state image pickup device, the control means
has a driving function in an all-pixel read mode for transferring
the signal electric charges from all the pixels of the solid state
image pickup device to the vertical registers to read pixel
signals, a driving function in a thinning read mode for
transferring the signal electric charges from a number n (n is one
or more positive integer) of pixels for each unit of a number m (m
is two or more positive integer) of pixels in the vertical
direction to the vertical registers to read pixel signals, and a
device shutter function for extracting the signal electric charges
from each pixel to control a photoelectric conversion time, the
control means being designed to carry out the operation of
extracting the signal electric charges from each pixel one or more
times immediately before the start of exposure when the solid state
image pickup device is driven in the all-pixel read mode directly
subsequent to the thinning read mode.
By carrying out the operation of extracting the signal electric
charges from each pixel one or more times immediately before the
start of exposure of the all-pixel read mode when the solid state
image pickup device its shifted in operation from the thinning read
mode to the all-pixel read mode, there can be provided an image
pickup apparatus in which signal electric charges accumulated in
the pixels, which are not read, due to multiple exposures during
the thinning read mode are surely purged out and prevented from
mixing in the all-pixel read mode.
Also, according to the present invention, in an image pickup
apparatus comprising a solid state image pickup device made up of a
plurality of pixels constituted by photoelectric transducers which
are two-dimensionally arrayed in the horizontal and vertical
directions, a vertical register for receiving signal electric
charges of each pixel and transferring the signal electric charges
in the vertical direction, and a horizontal register for
transferring the signal electric charges in the vertical register
in the horizontal direction, and control means for driving and
controlling the solid state image pickup device, the control means
has a driving function in an all-pixel read mode for transferring
the signal electric charges from all the pixels of the solid state
image pickup device to the vertical registers to read pixel
signals, a driving function in a thinning read mode for
transferring the signal electric charges from a number n (n is one
or more positive integer) of pixels for each unit of a number m (m
is two or more positive integer) of pixels in the vertical
direction to the vertical registers to read pixel signals, and a
device shutter function for extracting the signal electric charges
from each pixel to control a photoelectric conversion time, the
control means being designed to transfer the signal electric
charges from all the pixels to the vertical registers at the
beginning of the read period of one frame immediately before
starting to read the pixel signals of all the pixels when the solid
state image pickup device is driven in the all-pixel read mode
directly subsequent to the thinning read mode.
By transferring the signal electric charges from all the pixels to
the vertical registers at the beginning of the read period of one
frame immediately before starting to read the pixel signals of all
the pixels when the solid state image pickup device is shifted in
operation from the thinning read mode to the all-pixel read mode,
there can be provided an image pickup apparatus in which signal
electric charges are cleared up from all the pixels, allowing the
exposure to start from an empty state, and therefore signal
electric charges accumulated due to multiple exposures during the
thinning read mode are surely prevented from mixing in the
all-pixel read mode.
Still another object of the present invention is to provide an
image pickup apparatus which can prevent, at the time of shift from
the thinning read mode to the all-pixel read mode, the signal
electric charges remained in the thinning read mode from mixing in
the all-pixel read mode, and which can also remove smear components
leaking into the registers at the same time.
According to the present invention, in an image pickup apparatus
comprising a solid state image pickup device made up of a plurality
of pixels constituted by photoelectric transducers which are
two-dimensionally arrayed in the horizontal and vertical
directions, a vertical register for receiving signal electric
charges of each pixel and transferring the signal electric charges
in the vertical direction, and a horizontal register for
transferring the signal electric charges in the vertical register
in the horizontal direction, and control means for driving and
controlling the solid state image pickup device, the control means
has a driving function in an all-pixel read mode for transferring
the signal electric charges from all the pixels of the solid state
image pickup device to the vertical registers to read pixel
signals, a driving function in a thinning read mode for
transferring the signal electric charges from a number n (n is one
or more positive integer) of pixels for each unit of a number m (m
is two or more positive integer) of pixels in the vertical
direction to the vertical registers to read pixel signals, and a
device shutter function for extracting the signal electric charges
from each pixel to control a photoelectric conversion time, the
control means being designed to transfer the signal electric
charges from all the pixels to the vertical registers and then
transfer the signal electric charges in the vertical registers at a
high speed immediately before starting to read the pixel signals of
all the pixels when the solid state image pickup device is driven
in the all-pixel read mode directly subsequent to the thinning read
mode.
By transferring the signal electric charges from all the pixels to
the vertical registers immediately before starting to read the
pixel signals of all the pixels when the solid state image pickup
device is shifted in operation from the thinning read mode to the
all-pixel read mode, signal electric charges are cleared up from
all the pixels, allowing the exposure to start from an empty state,
and therefore signal electric charges accumulated due to multiple
exposures during the thinning read mode are surely prevented from
mixing in the all-pixel read mode. In addition, by transferring the
signal electric charges, which have been transferred to the
vertical registers, at a high speed for purge-out, smear components
leaking into the registers can be removed at the same time.
Still another object of the present invention is to provide an
image pickup apparatus which can reduce an amount of electric power
consumed in the operation of extracting signal electric charges
from each pixel for the device shutter function, while the
operation of extracting signal electric charges from each pixel is
surely achieved.
According to the present invention, in an image pickup apparatus
comprising a solid state image pickup device made up of a plurality
of pixels constituted by photoelectric transducers which are
two-dimensionally arrayed in the horizontal and vertical
directions, a vertical register for receiving signal electric
charges of each pixel and transferring the signal electric charges
in the vertical direction, and a horizontal register for
transferring the signal electric charges in the vertical register
in the horizontal direction, and control means for driving and
controlling the solid state image pickup device, the control means
has a device shutter function for extracting signal electric
charges from each pixel to control a photoelectric conversion time,
and performs the operation of extracting the signal electric
charges from each pixel a number n (n is one or more positive
integer) time(s) immediately before the start of exposure.
Hitherto, in a device shutter employed for outputting a motion
picture in image pickup apparatus (the term "device shutter" means
a function of variably setting a time during which electric charges
are generated upon irradiation of light and accumulated in a
photodiode constituting each pixel, and providing similar
advantages as those obtained by opening and closing a mechanical
shutter without needing any movable parts), the operation of
extracting signal electric charged from the pixel has been
performed by outputting a charge extracting pulse continuously from
the beginning of one frame to the time immediately before the start
of an exposure period in the same frame. Because the charge
extracting pulse is output continuously from the beginning of one
frame to the time immediately before the start of the exposure
period in the same frame, a large amount of electric power is
consumed. In contrast, with the present invention, by performing
the operation of extracting the signal electric charges from each
pixel a number n time(s) immediately before the start of exposure,
the large amount of electric power consumed can be reduced. Also,
by performing the operation of extracting the signal electric
charges from each pixel a number n time(s) immediately before the
start of exposure, the signal electric charges can be surely purged
out before the start of exposure. Further, the exposure period is
not affected by performing the charge extracting operation in such
a manner because the exposure period is given by a period from the
time at which the charge extracting operation is ended to the time
at which the accumulated signal electric charges are transferred to
the vertical register.
Still another object, of the present invention is to provide an
image pickup apparatus which can prevent signal electric charges
from overflowing into the charge transfer line even if excessively
strong light enters the photodiode, and which can produce a
satisfactory still picture free from noises.
According to the present invention, in an image pickup apparatus
comprising a solid state image pickup device made up of a plurality
of pixels constituted by photoelectric transducers which are
two-dimensionally arrayed in the horizontal and vertical
directions, a vertical register for receiving signal electric
charges of each pixel, and transferring the signal electric charges
in the vertical direction, and a horizontal register for
transferring the signal electric charges in the vertical register
in the horizontal direction, and control means for driving and
controlling the solid state image pickup device, the control means
has a device shutter function for extracting signal electric
charges from each pixel to control a photoelectric conversion time,
performs the operation of extracting the signal electric charges
from each pixel a number n (n is one or more positive integer)
time(s) immediately before the start of exposure during a read
period in which an output of the solid state image pickup device is
used to form a motion picture, and performs the operation of
extracting the signal electric charges from each pixel repeatedly
to inhibit an exposure operation during a read period in which the
output of the solid state image pickup device is used to form a
still picture.
If the read period in which the output of the solid state image
pickup device is used to form a still picture includes a period in
which the operation of extracting the signal electric charged from
the pixel is performed and a period in which that operation is not
performed, noises occur at the switching point between both the
periods and a horizontal streak appears in the still picture. In
contrast, with the present invention, by performing the operation
of extracting the signal electric charges from the pixel repeatedly
to inhibit the exposure operation during the read period in which
the output of the solid state image pickup device is used to form a
still picture, it is possible to prevent the occurrence of noises
and hence the occurrence of a horizontal streak. Also, when the
operation of extracting the signal electric charges is switched
over, the supply voltage is greatly varied at the switching point
and a horizontal streak appears due to a corresponding step
difference in brightness because the charge extracting pulse has a
high voltage. With the present invention, by continuously
performing the operation of extracting the signal electric charges,
the supply voltage is not varied during the period in which the
device output is used to form a still picture, and therefore a
satisfactory still picture output can be produced.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram showing the entire configuration of an
image pickup apparatus according to the present invention which is
applied to an electronic camera.
FIG. 2 is a timing chart for explaining the operation in a
conventional skipping read mode.
FIG. 3 is an illustration for explaining the read operation of a
CCD image pickup, device in the conventional skipping read
mode.
FIG. 4 is an illustration for explaining the device shutter
operation in the CCD image pickup device.
FIG. 5 is an illustration showing a overflown state of electric
charges accumulated due to multiple exposures in the conventional
skipping reads mode.
FIG. 6 is a timing chart for explaining a first embodiment of the
drive/control operation executed by a CPU in the electronic camera
shown in FIG. 1.
FIG. 7 is an illustration showing a state of electric charges
accumulated in the CCD image pickup device during the drive/control
operation shown in FIG. 6.
FIG. 8 is a timing chart for explaining the conventional operation
at the time of shift from the skipping read mode to an all-pixel
read mode.
FIG. 9 is an illustration for explaining the operation of the CCD
image pickup device at the time A in the timing chart of FIG.
8.
FIG. 10 is an illustration for explaining the operation of the CCD
image pickup device at the time B in the timing chart of FIG.
8.
FIG. 11 is a timing chart for explaining a second embodiment of the
drive/control operation executed by the CPU in the electronic
camera shown in FIG. 1.
FIG. 12 is a timing chart for explaining a third embodiment of the
drive/control operation executed by the CPU in the electronic
camera shown in FIG. 1.
FIG. 13 is an illustration for explaining the operation of the CCD
image pickup device at the time B in the timing charts of FIGS. 11
and 12.
FIG. 14 is a timing chart for explaining a fourth embodiment of the
drive/control operation executed by the CPU in the electronic
camera shown in FIG. 1.
FIG. 15 is a timing chart for explaining the operation to output a
motion picture by using a device shutter in a conventional image
pickup apparatus.
FIG. 16 is a timing chart for explaining a fifth embodiment of the
drive/control operation executed by the CPU in the electronic
camera shown in FIG. 1.
FIG. 17 is a timing chart for explaining the operation of the
conventional image pickup apparatus in a motion picture output mode
and a still picture record mode.
FIG. 18 is a timing chart for explaining a sixth embodiment of the
drive/control operation executed by the CPU in the electronic
camera shown in FIG. 1.
FIGS. 19A and 19B are illustrations showing examples of still
pictures formed by the operation in accordance with the timing
charts shown in FIGS. 17 and 18, respectively.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Preferred embodiments of the present invention will be described
below FIG. 1 is a block diagram showing the general configuration
of an image pickup apparatus according to the present invention
which is applied to an electronic camera. In FIG. 1, denoted by
reference numeral 1 is a CCD image pickup device for performing
photoelectric conversion, i.e., converting an optical signal into
an electric signal. A light enters the CCD image pickup device 1
through a lens (not shown) and a diaphragm 2. Denoted by 3 is a
correlation double sampling (CDS) circuit for removing noises from
an-output of the CCD image pickup device 1, and 4 is an amplifier
for amplifying an output of the correlation double sampling circuit
3. Denoted by 5 is an A/D converter for converting an output of the
amplifier 4 in the form of analog data into digital data, and 6 is
a processing circuit for processing, as image data, a signal from
the CCD image pickup device 1. Denoted by 7 is a DRAM for
temporarily storing the image data subjected to the signal
processing in the processing circuit 6, and 8 is a
compression/expansion circuit for compressing the image data stored
in the DRAM 7 and expanding the compressed data. The compressed
data is recorded in a recording medium 9, whereas the recorded data
read out of the recording medium 9 is expanded.
Further, denoted by 10 is an AF circuit for making focus control
using the image data obtained by processing the signal from the CCD
image pickup device 1, 11 is an AE circuit for making exposure
control, and 12 is an auto-white balancing (AWB) circuit for
setting a white balance. Denoted by 13 is a liquid crystal display
unit for displaying, on a liquid crystal screen, the image data
obtained by processing the signal from the CCD image pickup device
1. Denoted by 14 is an interface circuit for external display, i.e.
for displaying the image data on an external monitor or the like.
Denoted by 15 is a timing generator that generates timing pulses
for controlling the timed relation of the CCD image pickup device
1, etc., and 16 is an SG circuit for sending a synchronizing signal
to the timing generator 15. Denoted by 17 is a CPU for controlling
the operation of all the above components.
In the electronic camera thus constructed, the electric signal
resulted from the photoelectric conversion in the CCD image pickup
device 1 passes the correlation double sampling circuit 3, the
amplifier 4 and the A/D converter 5, and is then subjected to the
signal processing in the processing circuit 6 for conversion into
an image signal. The image signal is first recorded in the
recording medium 9 and displayed in the liquid crystal display unit
13 to achieve matching of the angle of field for determining what a
still picture is to be recorded. Finally, the image signal is
recorded as a still picture in the recording medium 9.
A first embodiment of the drive/control operation of the CCD image
pickup device executed by the CPU 17 will be described below. This
first embodiment corresponds to a first aspect of the present
invention. With the CCD image pickup device constructed of a large
number of pixels, as mentioned before, in such an operation as
requiring high-speed processing that is needed, e.g., when an image
is to be displayed in the liquid crystal display unit and when the
AE or AF operation is to be carried out, except the time of
recording a still picture, the high-speed processing is performed
in a skipping read mode (thinning read mode) because slow-speed
processing in an all-pixel read mode takes a longer-period of
time.
The operation in a conventional skipping read mode will now be
described with reference to a timing chart of FIG. 2 and an
illustration of FIG. 3 for explaining the read operation of the CCD
image pickup device. In FIG. 2, VD represents a vertical
synchronizing signal, and a transfer pulse 1 is a pulse for
transferring signal electric charges of pixels (photodiodes) 101 of
each line 1 to corresponding vertical registers 103 in the CCD
image pickup device, as shown in FIG. 3. Likewise, a transfer pulse
2 is a pulse for transferring signal electric charges of pixels 102
of each line 2 to corresponding vertical registers 103. A charge
extracting pulse is a pulse for, as shown in FIG. 4, changing a
potential Vsub of a silicon substrate 111 in the CCD image pickup
device to Vsub' to lower a potential barrier 112, and purging out
all electric charges 114, which are accumulated in a photodiode 113
constituting a pixel, to the silicon substrate 111 so that no
electric charges 114 are accumulated in the photodiode 113.
Additionally, in FIG. 4, 115 denotes a vertical register and 116
denotes a CCD surface.
In FIG. 2, an exposure period represented by a high-level is a
period during which light enters the CCD image pickup device and
electric charges are accumulated therein. When a device shutter is
used, exposure is not made over a full period of one frame.
Specifically, the charge extracting pulse is output for each
predetermined period in one frame, and the exposure period is
shorter than the full period of one frame. When a device shutter is
not used, the charge extracting pulse is not output and exposure is
made over the full period of one frame until signal electric
charges are transferred from the pixel to the vertical register in
response to the transfer pulse.
In the skipping read mode, as shown in FIG. 2, the transfer pulse 1
is output for each vertical synchronizing pulse VD (in units of one
frame), but the transfer pulse 2 is not output at all. Accordingly,
as shown in FIG. 3, signal electric charges of only the pixels 101
of the line 1 are transferred to the vertical registers 103, but no
electric charges of the pixels 102 of the line 2 are transferred to
the vertical registers 103. Note that the case where the transfer
pulse 2 is also output for each frame corresponds to the all-pixel
read mode. Thus, in the skipping read mode, since signal electric
charges of only the pixels 101 of the line 1 are transferred to the
vertical registers 103, the electric charges in the vertical
registers 103 are moved under double-transfer operation, i.e.,
carried over two pixels for each operation, followed by transfer
into a horizontal register 104. A CCD output is then produced from
the horizontal register 104.
If the above-described operation in the skipping read mode is
repeated, signal electric charges are accumulated in the
photodiodes constituting the pixels of the line 2 and continue
accumulating there without being transferred to the vertical
registers. Thus in the conventional skipping read mode, as shown in
FIG. 5, the signal electric charges tend to accumulate in excess of
the capacity of each photodiode and are more likely to overflow
into the vertical register.
To avoid such a problem, as shown in a timing chart of FIG. 6, this
first embodiment is designed to always apply the charge extracting
pulse at the beginning of each frame in the skipping read mode. In
other words, the charge extracting pulse is applied at the
beginning of each frame even when the device shutter is not used.
At the start-up of each exposure, therefore, the electric charges
in the photodiode are all purged out to the substrate, as shown in
FIG. 7, allowing the exposure to start in a condition where no
electric charges are accumulated in the photodiode. Consequently,
for the pixels of the line 2 to which the transfer pulse 2 is not
applied for reading of signal electric charges, the electric
charges are purged out to the substrate at least once for each
frame, and hence are surely prevented from overflowing into the
vertical registers.
A second embodiment of the drive/control operation of the CCD image
pickup device executed by the CPU will be described below. This
second embodiment corresponds to a second aspect of the present
invention. Generally, in electronic cameras, matching of the angle
of field is achieved by first effecting the operation of displaying
an object image on a liquid crystal screen with a liquid crystal
display unit or the like, and then effecting the operation of
recording the object image, as a still picture frame, in a
recording medium upon a shutter button being pushed. When
displaying the object image in the liquid crystal display unit, a
skipping read mode is used so as to carry out signal processing at
a high speed and to display. On the other hand, when recording a
still picture in the recording medium, an all-pixel read mode is
used to improve image quality of the recorded frame.
Thus, in electronic cameras, a still picture is recorded in the
recording medium by switching over from the skipping read mode to
the all-pixel read mode. FIG. 8 is a timing chart, for explaining
the conventional operation at the time of shift from the skipping
read mode to the all-pixel read mode. In FIG. 8, a shutter trigger
is a pulse output upon a shutter button being pushed. Until the
shutter button is pushed, the CCD image pickup device continues
operation in the skipping read mode. Then, when the shutter button
is pushed and the shutter pulse is output, the operation of the CCD
image pickup device shifts to the all-pixel read mode after the VD
pulse (vertical synchronizing pulse) output next, thereby starting
the operation of recording a still picture.
During the skipping read mode, as described above in connection
with the first embodiment, only the transfer pulse 1 is output at
the beginning of one frame, but the transfer pulse 2 is not output
at all. Also, during the skipping read mode, the device shutter is
not used, and therefore the charge extracting pulse is not output
at all.
When the shutter trigger is output and the skipping read mode is
shifted to the all-pixel read mode, the CCD image pickup device
operates in an exposure mode, where light enters the CCD image
pickup device and electric charges are accumulated in pixels, in a
first period of the VD pulse after the shift to the all-pixel read
mode. The electric charges accumulated in the period of the
exposure mode are then read in a period of the next read mode. In
the above process, when the operation is shifted from the exposure
mode to the read mode under the all-pixel read mode, both the
transfer pulses 1 and 2 are applied to read all the pixels.
FIG. 9 illustrates the read operation of the CCD image pickup
device at the time A in the timing chart of FIG. 8, i.e., at the
time of shift from the skipping read mode to the exposure mode
under the all-pixel read mode. In the skipping read mode, electric
charges are not transferred from the photodiodes constituting the
pixels 102 of the line 2 to the vertical registers 103. Hence,
electric charges are transferred from only the pixels 101 of the
line 1, and electric charges remain left in the photodiodes
constituting the pixels 102 of the line 2. At the time B in the
timing chart of FIG. 8, i.e., at the time of shift from the
exposure mode to the read mode under the all-pixel read mode, both
the transfer pulses 1 and 2 are output to read all the pixels, as
shown in FIG. 8, whereupon electric charges are transferred from
all the pixels to the vertical registers 103, as shown in FIG. 10.
On this occasion, however, because the operation of reading or
extracting electric charges is not performed on the pixels 102 of
the line 2 in the skipping read mode without the device shutter
operation, electric charges generated due to multiple exposures are
accumulated in the pixels 102, and therefore signal electric
charges generated in different exposure times are output when the
electric charges are transferred from both the lines 1 and 2.
To avoid such a problem, as shown in a timing chart of FIG. 11,
this second embodiment is designed such that when the shutter
trigger is output and the skipping read mode is shifted to the
all-pixel read mode, the charge extracting pulse, which has not
been output during the skipping read mode, is output at least once
immediately after the shift from the skipping read mode to the
all-pixel read mode. By applying the charge extracting pulse,
electric charges accumulated in the photodiodes of all the pixels
are once purged out thoroughly so that, in the exposure mode under
the all-pixel read mode, exposure starts to accumulate electric
charges from a condition where no electric charges are accumulated
in any pixels. Accordingly, when the read operation from all the
pixels is performed by outputting both the transfer pulses 1 and 2
in the read period under the all-pixel read mode, the problem
described above in connection with FIG. 10, i.e., the problem that
signal electric charges are output at different exposure levels, is
avoided. Further, a still picture can be likewise recorded
regardless of change in shutter speed.
A third embodiment of the drive/control operation of the CCD image
pickup device executed by the CPU will be described below with
reference to FIG. 12. This third embodiment corresponds to a third
aspect of the present invention.
As with the second embodiment shown in FIG. 11, the third
embodiment intends to avoid exposure levels for the respective
lines from differing from each other at the time of shift from the
exposure mode to the read mode under the all-pixel read mode.
Comparing the second embodiment shown in FIG. 11 wherein the charge
extracting pulse is output immediately after the shift from the
skipping read mode to the all-pixel read mode, the third embodiment
is different in that when the shutter trigger is output and the
skipping read mode is shifted to the all-pixel read mode, the,
transfer pulse 2 is also output along with the transfer pulse 1
immediately before the exposure mode under the all-pixel read mode
starts. By applying both the transfer pulses 1 and 2, electric
charges in the photodiodes of all the pixels are transferred to the
vertical registers in a like manner to the all-pixel read mode
prior to the period of the exposure mode, followed by being
transferred to the horizontal register. The electric charges
accumulated in all of the photodiodes and the vertical registers
are cleared up. After that, both the transfer pulses 1 and 2 are
output again at the beginning of the read mode, whereupon signal
electric charges accumulated during the period of the exposure mode
are transferred from all the photodiodes to the vertical registers
for achieving the read operation from all the pixels.
FIG. 13 illustrates the read operation of the CCD image pickup
device at the time B in the timing charts of the second and third
embodiments shown respectively in FIGS. 11 and 12, i.e., at the
beginning of the read mode. In the read operation of the CCD image
pickup device at the time B, i.e., at the beginning of the read
mode, according to the conventional process shown in FIG. 8, the
lines 1 and 2 have different exposure times from each other, as
shown in FIG. 10, because the line 2 is subjected to multiple
exposures. By contrast, in the second and third embodiments of the
present invention, since no electric charges are accumulated in any
photodiodes at the beginning of the exposure mode, electric charges
accumulated in the same exposure time regardless of the lines can
be read at the beginning of the read mode, as shown in FIG. 13.
Thus, in the second and third embodiments shown in FIGS. 11 and 12,
it is possible to read electric charges accumulated in the same
exposure time regardless of the lines at the time of shift from the
skipping read mode to the all-pixel read mode.
A fourth embodiment of the drive/control operation of the CCD image
pickup device executed by the CPU will be described below with
reference to FIG. 14. This fourth embodiment corresponds to a
fourth aspect of the present invention. When both the transfer
pulses 1 and 2 are output to read signal electric charges of all
the pixels at the time of shift from the skipping read mode to the
all-pixel read mode like the third embodiment shown in FIG. 12,
signal electric charges are transferred from all the photodiodes to
the vertical registers; hence all the photodiodes are deprived of
electric charges accumulated so far therein. However, the electric
charges transferred from the photodiodes to the vertical registers
still remain in the vertical registers immediately after the
transfer to there. The electric charges transferred and remaining
in the vertical registers are useless, and the electric charges
transferred from the photodiodes constituting the pixels of the
line 2 are particularly useless because they are generated due to
multiple exposures. The electric charges transferred to the
vertical registers are therefore all once output to the outside
within the period of the exposure mode.
With the above in mind, in this fourth embodiment, after signal
electric charges have been transferred from the photodiodes of all
the pixels to the vertical registers as with the third embodiment
shown in FIG. 12, all the useless electric charges in the vertical
registers are transferred at a high speed for purge-out within the
period of the exposure mode. By so transferring the useless
electric charges at a high speed to be swept away from the vertical
registers repeatedly, smear components leaking into the registers
can also be removed at the same time.
A fifth embodiment will be described below. This fifth embodiment
corresponds to a fifth aspect of the present invention. In general,
when a motion picture is output in an electronic camera by using
device shutters, one frame is formed per VD (vertical synchronizing
signal) shown in FIG. 15. More specifically, a transfer pulse is
output per VD to transfer signal electric charges, which are
accumulated in photodiodes, to vertical registers. In the next
period of one frame, resulting image data is then displayed. When
the device shutter is used, a charge extracting pulse is always
output from the beginning of each frame until the time to start
exposure, as shown in FIG. 15, for thereby setting an exposure
period required for operating the device shutter. Upon reaching the
time to start exposure that is determined for setting the required
exposure period, the charge extracting pulse is stopped from being
output. A period from the time to start exposure to the time to
output the next transfer pulse is given as the exposure period
during which electric charges are accumulated in the
photodiode.
However, the charge extracting pulse used for operating the device
shutter has a high voltage and is output in a large number. A large
amount of electric power is consumed correspondingly, as shown in
FIG. 15, and hence the battery life is shortened.
With the above in mind, in this fifth embodiment, the charge
extracting pulse is not output so many and held at a necessary
minimum number, as shown in FIG. 16. In the case of operating the
device shutter, the exposure period from the time to stop the
output of the charge extracting pulse to the time to output the
next transfer pulse is important. In a period before the exposure
period, therefore, it is not necessary to output the charge
extracting pulse all over such a preceding period. In other words,
it is just required to output at least one charge extracting pulse
for purging out the electric charges immediately before reaching
the time to start exposure that is determined for setting the
required exposure period. By so outputting the charge extracting
pulse, a period from the time at which the electric charges are
purged out to the time at which the next transfer pulse is output
is given as the exposure period during which electric charges
generated during the predetermined shutter operation are
accumulated in the photodiode.
Thus, in this fifth embodiment, the charge extracting pulse is not
output all over the period from the beginning of each frame to the
time to start exposure, but output at least once immediately before
the time to start exposure. Although the charge extracting pulse is
output three times in FIG. 16, it is preferably required to output
the charge extracting pulse two or more times. By so outputting the
charge extracting pulse, even if electric charges are not
completely purged out upon the first pulse being output, the
remaining electric charges are surely purged out upon the
subsequent pulses being output. As a result, precise electric
charges can be accumulated in the exposure period based on the
device shutter operation while reducing an amount of consumed
electric power.
A sixth embodiment will be described below. This sixth embodiment
corresponds to a sixth aspect of the present invention. Generally,
an electronic camera is operated such that a motion picture is
output to a liquid crystal display unit and a monitor connected via
a cable until a shutter button is pushed, and a still picture is
recorded in a recording medium upon the shutter button being
pushed. FIG. 17 is a timing chart for explaining the operation of
the conventional image pickup device in a motion picture output
mode for outputting a motion picture and a still picture record
mode for recording a still picture. As shown in FIG. 17, when the
shutter button is pushed and the shutter trigger is output, the
operation shifts from the motion picture output mode to the still
picture record mode. A period of the still picture record mode
consists of a period of an exposure mode in which light enters the
CCD image pickup device, and a period of a read mode in which
electric charges accumulated in the exposure period are read and
recorded as a still picture. During the period of the read mode
under the still picture record mode, the electric charges generated
due to exposure in the preceding period of the exposure mode are
read. When the period of the read mode is completed, a still
picture is recorded, followed by shift to the next motion picture
output mode. In the conventional apparatus, therefore, an exposure
period is also provided in the period of the read mode as shown at
4 in FIG. 17, and electric charges generated due to exposure in the
period 4 are read in the motion picture output mode to form the
next frame.
However, the above conventional method of providing the exposure
period in the period of the read mode, there arises a problem
below. Because the charge extracting pulse is not output in the
exposure period, the period of the read mode necessarily includes a
period in which the charge extracting pulse is output and a period
in which it is not output. The voltage of the charge extracting
pulse is so high that the supply voltage is greatly varied at the
boundary between the period in which the charge extracting pulse is
output and the period in which it is not output, thereby giving
rise to noises or the like. This results in that a horizontal
streak 122 occurs in an output displayed as a still picture frame
121 at the timing corresponding to the above boundary, as shown in
FIG. 19A.
To prevent such a horizontal streak from appearing in the still
picture frame, in this sixth embodiment, the charge extracting
pulse is continuously output all over the period of the read mode
under the still picture record mode so that the exposure period is
eliminated to inhibit electric charges from being accumulated in
the photodiode during the read mode, as shown in FIG. 18. With this
modification, the period of the read mode is avoided from including
both the period in which the charge extracting pulse is output and
the period in which it is not output, and the charge extracting
pulse is continuously output all over the read period, resulting in
that voltage variations do not occur and a horizontal streak does
not appear in the still picture frame, as shown in FIG. 19B.
Further, because of the charge extracting pulse being always output
during the read period, even if excessively strong light partly
enters the photodiode, useless electric charges are prevented from
overflowing from the photodiode into the charge transfer line. It
is to be noted that, in this sixth embodiment, since the charge
extracting pulse is continuously output all over the period of the
read mode under the still picture record mode and the exposure
period in which electric charges generated due to exposure are
accumulated to be read in the motion picture output mode subsequent
to the still picture record mode is not provided, a first frame is
not output in the motion picture output mode subsequent to the
still picture record mode. However, immediately after the end of
the read period in the still picture record mode, processing for
the record operation on the recording medium, etc. are performed
and the next image pickup operation is not started at once. Thus,
there arise no problem despite that the motion picture output of
one frame is not produced.
As described above in connection with the preferred embodiments,
the present invention can provide the advantages below. According
to the first aspect of the present invention, since the operation
of extracting the signal electric charges from each pixel is
carried out one or more times for each read period of one frame
when the image pickup device is driven in the thinning read mode,
it is possible to prevent overflow of signal electric charges from
the pixels, that is otherwise caused during the operation in the
thinning read mode; hence interlaced scanning is no longer needed
and the occurrence of flickers is avoided. According to the second
aspect of the present invention, since the operation of extracting
the signal electric charges from each pixel is carried out one or
more times immediately before the start of exposure in the
all-pixel read mode when the image pickup device is shifted in
operation from the thinning read mode to the all-pixel read mode,
signal electric charges accumulated in the pixels due to multiple
exposures during the thinning read mode are surely purged out and
prevented from mixing in the all-pixel read mode. According to the
third aspect of the present invention, since the signal electric
charges are transferred from all the pixels to the vertical
registers at the beginning of the read period of one frame
immediately before starting to read the pixel signals of all the
pixels when the image pickup device is shifted in operation from
the thinning read mode to the all-pixel read mode, the exposure can
be started in an empty condition where electric charges are cleared
up from all the pixels, and therefore signal electric charges
accumulated due to multiple exposures during the thinning read mode
are surely prevented from mixing in the all-pixel read mode.
Also, according to the fourth aspect of the present invention,
since the signal electric charges are transferred from all the
pixels to the vertical registers and the signal electric charges in
the vertical registers are then transferred at a high speed for
purge-out immediately before starting to read the pixel signals of
all the pixels when the solid state image pickup device is shifted
in operation from the thinning read mode to the all-pixel read
mode, the exposure can be started in an empty condition where
electric charges are cleared up from all the pixels, and therefore
signal electric charges accumulated due to multiple exposures
during the thinning read mode are surely prevented from mixing in
the all-pixel read mode. In addition, smear components leaking into
the vertical registers can be removed at the same time. According
to the fifth aspect of the present invention, since the operation
of extracting the signal electric charges from each pixel for the
device shutter function is performed a number n time(s) immediately
before the start of exposure, the signal electric charges can be
surely purged out before the start of exposure while reducing the
large amount of electric power consumed. According to the sixth
aspect of the present invention, since the operation of extracting
the signal electric charges from the pixel is performed repeatedly
to inhibit the exposure operation during the read period in which
the output of the image pickup device is used to form a still
picture, it is possible to prevent the occurrence of noises and
hence the occurrence of a horizontal streak at the point in time at
which the operation of extracting the signal electric charges is
switched over.
* * * * *